Friday, October 17, 2008

What You Can See On The Moon?

Even if you don’t have a telescope, there are some very interesting lunar observations you can make. Have you ever thought that the moon looks bigger when it’s closer to the horizon? It’s just an optical illusion, but you can test it out. The angular size of the moon is surprisingly small. A circular piece of paper just about 0.2 inches in diameter held at arms’ length should cover the moon. At the next full moon, cut out a little disk of that size and prove to yourself that the moon stays the same size as it rises high into the sky.The telescope through which Galileo Galilei made his remarkable lunar observations was a brand-new and very rare instrument in 1609; but you can easily surpass the quality of his observations with even a modest amateur instrument.Why is it so exciting to point your telescope at the moon?Because no other celestial object is so close to us. Being so close, the moon provides the most detailed images of an extraterrestrial geography that you will ever see through your own telescope.When should you look at the moon?The easy answer is: anytime the sky is reasonably clear. But if you’re thinking that you should always wait until the moon is full, think again. When is the best time to view a rugged Earthly landscape at its most dramatic? When the sun is low, early in the morning or late in the afternoon, and the light rakes across the earth, so that shadows are cast long and all stands in bold relief.The same holds true for the moon. When you can see the sunrise or sunset line (the terminator), and the moon is not so full as to be blindingly bright, that is when the topography of the moon will leap out at you most vividly. This characteristic means that you’ll get some very satisfying viewing when the moon is at one of its crescent phases, and probably not at its full phase.